Jennifer McGuire remembers how, as a child, she would order only certain things at restaurants because they would be easier to say. McGuire, 30, has stuttered for as long as she can remember.

"Stuttering has colored my whole life," she said Saturday. "Only recently has it not been the first thing I think about when I get up in the morning and the last thing before I go to bed."

Stuttering typically starts around 2 to 4 years of age, after the stutterer already had learned language, which is why legendary psychoanalysist Sigmund Freud thought it had something to do with parenting or something else in the environment.

But scientists have found copious evidence that biological mechanisms in the brain can explain stuttering. They presented some of the more recent findings at the American Association for the Advancement of Science meeting in Washington, D.C.

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